DOS attacks?

Anyone think of a good reason why we suddenly appear to be under attack, with our Netgear router sending batches of alerts every 20-30 minutes or so as below. Normally I'd get one of these maybe once a day, but the last 24 hours have gone mad...<pre>TCP Packet - Source:66.120.47.82,17556 Destination:xxx.xxx.xxx.xxx,445 - [DOS]
TCP Packet - Source:66.120.47.82,17557 Destination:xxx.xxx.xxx.xxx,3127 - [DOS]</pre>

We'll get around 10-20 coming in from one IP address, all quiet for a while, then another batch from another address....